carbonate mineral
Carbonate minerals are those minerals containing the carbonate ion, .
Carbonate divisions Anhydrous carbonates
*Calcite group: trigonal
**Calcite CaCO3
**Gaspéite (Ni,Mg,Fe2+)CO3
**Magnesite MgCO3
**Otavite CdCO3
**Rhodochrosite MnCO3
**Sider ...
with the
chemical formula
A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...
Mg4Al2(OH)12CO3⋅3H2O.
The mineral was named after Quintin Wight of Ottawa, Ontario, Canada (b. 1935), who was a significant contributor to mineral studies at
Mont Saint-Hilaire
Mont Saint-Hilaire (; English: Mount Saint-Hilaire; ;, ; see for other names) is a mountain, high, in the Montérégie region of southern Quebec. It is about thirty kilometres east of Montreal, and immediately east of the Richelieu River. It ...
.
Quintinite is found as 2H and 3T, or 2-hexagonal and 3-trigonal,
polytypes
In crystallography, polymorphism is the phenomenon where a compound or element can crystallize into more than one crystal structure.
The preceding definition has evolved over many years and is still under discussion today. Discussion of the defi ...
, which were originally approved as separate species, but have not been considered species since 1998.Bernard, J.H. and Hyrsl, J. (2004) Minerals and their Localities, 807 p. Granit, s.r.o., Prague (Quintinite, p. 503). These hexagonal and trigonal forms of quintinite are both from the hexagonal crystal systems, meaning they both have similar lengths of their crystal axes and the same angles between these axes. As a hexagonal mineral, quintinite has three axes of equal length at 60 degree angles to one another and a c axis perpendicular to these three axes of a different length. 2H occurs in
carbonatite
Carbonatite () is a type of intrusive rock, intrusive or extrusive rock, extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geoche ...
São Paulo
São Paulo (; ; Portuguese for 'Paul the Apostle, Saint Paul') is the capital of the São Paulo (state), state of São Paulo, as well as the List of cities in Brazil by population, most populous city in Brazil, the List of largest cities in the ...
,
Brazil
Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
, in the Jacupiranga mine and 3T occurs with minerals like gonnardite and donnayite. Both polytypes occur in
hydrothermal vent
Hydrothermal vents are fissures on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hot ...
s in alkaline rocks. Herg (1977) interpreted the Jacupiranga area as related to a hotspot. The 3T polytype was originally found in the Poudrette quarry at
Mont Saint-Hilaire
Mont Saint-Hilaire (; English: Mount Saint-Hilaire; ;, ; see for other names) is a mountain, high, in the Montérégie region of southern Quebec. It is about thirty kilometres east of Montreal, and immediately east of the Richelieu River. It ...
petrographic microscope
A petrographic microscope is a type of optical microscope used to identify Rock (geology), rocks and minerals in thin sections. The microscope is used in optical mineralogy and petrography, a branch of petrology which focuses on detailed descr ...
. The 3T polytype, however, is not commonly pleochroic but can show green
pleochroism
Pleochroism is an optical phenomenon in which a substance has different colors when observed at different angles, especially with Polarization (waves), polarized light.
Etymology
The roots of the word are from Greek (). It was first made compou ...
if it is high in iron. The 3T polytype has a positive index of refraction whereas the 2H polytype can possess crystals with either a positive or a negative index of refraction.